Method and apparatus for surface treatment of workpiece



Y. G. HURD Jan. 27, 1970 METHOD AND APPARATUS FOR SURFACE TREATMENT OF WORKPIECE Filed Nov. 1; 1967 S Sheets-Sheet 1 INVENTOR. )fiQ/ K Hum J- a l," lm Afro/easy v Jan. 27, 1970 Y. G. HURD 3,49

METHOD AND APPARATUS FOR SURFACE TREATMENT OF WORKPIECE Filed Nov. 1, 1967 3 Sheets-Sheet 2 Jan.27,1970 Y. G. HURD 3,491,566

METHOD AND APPARATUS FOR SURFACE TREATMENT OF WORKPIECE Filed Nov. 1, 1967 3 Sheets-Sheet 3 United States Patent O 3,491,566 METHOD AND APPARATUS FOR SURFACE TREATMENT OF WORKPIECE Yorick G. Hurd, Mamaroneck, N.Y., assignor to L. E. Carpenter & Company, Wharton, N.J., a corporation of Delaware Filed Nov. 1, 1967, Ser. No. 679,842

Int. Cl. BZlj /06 US. Cl. 7276 12 Claims ABSTRACT OF THE DISCLOSURE Apparatus and method for making an embossing roll. Cylindrical workpiece of relatively soft material is rotated on its axis and its surface is indented by relatively hard hammer means acting at a limited locality. Hammer means mounted on carriage movable lengthwise of workpiece. Rotation of workpiece and carriage movement are in timed relation. Hammer means has plurality of tips spaced peripherally of workpiece, and timing of hammer strokes with respect to workpiece rotation controls number of strokes on each indentation. Hammer tips may be lens shaped, and embossing roll is then covered with lenticules. Angle of hammer strokes against roll may be varied progressively from end to end of roll. Finished roll is then useful for making projection screens.

BACKGROUND OF THE INVENTION This invention relates to the formation of ornamental or utilitarian surfaces on metal workpieces. It is disclosed herein as being particularly useful in the manufacture of embossing rolls.

In the prior art, there are two principal commercial methods for making embossing rolls. One method involves the preparation of a small master tool corresponding in contour to a small section or pattern repeat of the final roll desired. This tool is first made in mild steel which is then heat treated to give it a hardened surface. The hardened tool is then repeatedly forced into the surface of a softer metal roll, being stepped along the roll to repeat the pattern along the length of the roll, and also being stepped around the roll to repeat the pattern around the roll periphery. The first roll so formed is usually hardened and then used to impress the pattern in a larger roll. The surface of that roll may be plated and is then ready to be used in embossing.

The other commonly used method for making an embossing roll is by electroforming. Typically, a sheet of material whose pattern it is desired to reproduce is formed into a sleeve. The inside surface of the sleeve is then covered with a metallic surface, for example, as by chemical deposition of silver. The silver coating is then used as an electrode to build up electrolytically a substantial thickness of copper, after which the original sheet material defining the pattern may be removed. A suitable hard coating, e.g., chromium, is then deposited on the copper electrolytically, completing the formation of an embossing roll.

RELATED APPLICATION There is shown and described in the copending application of George Lucas, Jr. and Yorick G. Hurd, Ser. No. 679,796 filed Nov. 1, 1967, a projection screen having a lenticular surface, in which the lenticules are arranged in horizontal rows, with the vertical tilt of the lenticules in each row varying progressively from top to bottom of the screen, but with the horizontal orientation of the lenticules in any horizontal row substantially the same.

SUMMARY OF THE INVENTION The present invention is directed to a method and apparatus for making an embossing roll. It is particularly useful for making an embossing roll to produce a projection screen of the type described in the Lucas and Hurd application, mentioned above. Nevertheless, the invention is not necessarily limited to the production of embossing rolls for making projection screens, but may be used for producing embossing rolls for other purposes, e.g., for the manufacture of sheet material having an embossed ornamental surface.

The apparatus of the invention may best be described as being similar to a lathe, including a headstock and tailstock between which a cylinder to be made into an embossing roll is mounted and by which the cylinder is rotated. A tool holding carriage is driven lengthwise of the cylinder and its movements are coordinated with the rotation of the cylinder. The tool means on the carriage comprises one or more hammers. The hammers are reciprocated by a motor also supported on the carriage and coordinated with the motor which rotates the workpiece and drives the tool lengthwise. In the particular apparatus shown, the hammers are reciprocated by a cam driven by the motor. The cam is effective periodically to lift the hammers away from the workpiece for a predetermined distance and thereafter to let them fall against the workpiece, thereby indenting its surface.

The hammers, their driving motor, and the cam mechcham'sm are all mounted on a plate connected to the carriage for rotation about a pivot axis aligned with the tips of the hammers and rotated on its pivot by means of a guide rail extending lengthwise of the cylinder and angularly adjustable. By adjusting the guide rail, the angle of the hammer strokes against the roll surface may be varied. For the purpose of making an embossing roll to produce a projection screen of the type described, it is preferred to vary the angle of the hammer strokes progressively from end to end of the roll.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of an apparatus constructed in accordance with the invention;

FIG. 2 is a fragmentary plan View of a portion of the apparatus of FIG. 1, on an enlarged scale, taken on the line 2-2 of FIG. 1;

FIG. 3 is a partial cross-sectional view taken on the line 3-3 of FIG. 1;

FIG. 4 is a fragmentary rear elevational view, showing the hammer means in three different positions with respect to the embossing roll;

FIG. 5 is a greatly enlarged cross-sectional view similar to a portion of FIG. 3, showing the hammer means in contact with the workpiece;

FIG. 5A is an enlarged sectional view taken on the line 5A5A of FIG. 5, showing one hammer tip;

FIG. 5B is a similarly enlarged sectional view taken on the line 5B5B of FIG. 5A;

FIG. 6 is a developed sectional view taken on the line 6-6 of FIG. 5;

FIG. 7 is an enlarged fragmentary view of the embossing roll of FIG. 4, showing in detail the surface structure and the effect of the hammers in three different positions;

FIG. 8 is a somewhat diagrammatic view of an embossing apparatus employing a roll manufactured in accordance with the invention;

FIG. 9 is an enlarged fragmentary view showing the material being embossed at the bite of the rolls in FIG. 8;

FIG. 10 is an elevational view of a finished projection screen made by the roll of FIGS. 8 and 9; and

FIG. 11 is a fragmentary cross-sectional view taken on the line 11--11 of FIG. 10, and greatly enlarged.

As pointed out in the copending application of Lucas and Hurd, mentioned above, a projection screen constructed in accordance with that invention must be made so as to avoid regularly recurring errors in the lenticule formation, which might otherwise result in the formation of a bright or dull spot in the screen, or in the formation of a bright or dull line in the screen. It is therefore necessary that the method and apparatus used for making the embossing roll be effective to produce an embossing roll without regularly recurring errors. Numerous structural features of the apparatus described herein are particularly intended for the prevention of such regularly recurring errors.

There is shown in FIG. 1, a machine tool similar to a lathe, having a bed 1 supporting a headstock 2 and a tailstock 3. A workpiece 4 in the form of a copper cylinder to be made into an embossing roll is supported between the headstock 2 and the tailstock 3. t

A carriage 5 is slidably mounted on a rail 6, along which it is driven by a rotatable lead screw 7. The lead screw 7 is connected through a speed reducer 8 to the rotating parts of the headstock 2 for concurrent movement therewith.

The headstock 2 has a shaft 9 supporting a chuck 10 which carries one end of the workpiece 4. The other end of the workpiece is carried on a suitable center 11 or steady rest in the tailstock 3. The shaft 9 is driven by a motor 12 through a belt 13. Another belt 14 connects the shaft 9 to the speed reducer 8 which drives the lead screw 7.

The belts in these drives assist in avoiding the repetition of regularly recurring errors in the finished embossing roll. Gears, unless very carefully manufactured, have inherent errors, which appear at one particular spot on the periphery of each gear and which result in regularly repeated errors in the embossing roll. However, when belt drives are used, the regularly repeated errors are avoided, even though it is practically certain that random errors are introduced due to the slippage of the belt. Consequently, it is possible to use cheaper gears if a belt is introduced into the driving mechanism. Random errors can be tolerated in the manufacture of embossing rolls for making projection screens, whereas regularly repeated errors must be avoided. If the embossing roll is to be used for some other purpose, e.g., for making ornamental sheet material, then the regularly repeated errors may possibly be tolerated.

Mounted on the carriage 5 is an angle plate 15. A vertical plate 16 is pivoted on the vertical flange of the angle plate 15 for rotation about a pivot axis 17. A generally horizontal plate 16a is welded to the vertical plate 16 and supports a motor 18 driving a cam 19 which engages the under side of a follower arm 20 mounted on a pivot 21 (FIG. 2) supported on the plate 16. At its right-hand end, as viewed in FIGS. 1 and 2, the arm 20 has a downwardly extending projection 20a, on the lower end of which are afiixed three hammers 22, which are substantially aligned with the pivot axis 17. As best seen in FIG. 5, the lower ends of the hammers 22 are tapered, and terminate respectively in noses 22a, 22b, 220, of rectangular cross-section, each having a cylindrical surface on its lower end, as shown in FIGS. 5, 5A and 5B. The axes of these cylindrical surfaces are parallel to the axes of the cylindrical workpiece 4. The noses of the hammers are made somewhat wider, in the direction perpendicular to the axis of the roll, than the desired lenticular contour to be produced. Thus the edges of the hammers overlap the adjacent lenticules, and flats between the lenticules are avoided.

Other contours may be employed on the faces of the hammer tips.

The motor 18 is part of a selsyn system whose generator 23 is driven by the motor 12, so that the hammers 22 are reciprocated in timed relation to the rotation of the workpiece 14. Due to the presence of the belt 13,

the hammers 22 and the workpiece are not exactly synchronized in order to avoid the presence of repeated errors as mentioned above.

The plate 16 supports an arbor 24 on which is journaled a roller follower 25. The follower 25 rides on the upper surface of a guide rail 26, which may be regarded as a type of cam. The right-hand end of the guide rail 26, as viewed in FIG. 1, is fastened by a bolt 27, adjustable in crossed slots in the guide rail 26 and in a column 3a extending upwardly from the tailstock 3. The left-hand end of a guide rail 26 is mounted on a bolt 28 adjustable in a vertical slot formed in a column 29 supported by the headstock 2, and in a horizontal slot in the guide rail 26. The bolts 27 and 28 may be fastened in any position along their respective slots, for example, by means of a head on the bolt, a thread on the opposite end, and a wing nut (not shown).

Instead of lifting the hammers and allowing them to drop by gravity, they could alternatively be driven positively against the workpiece, or their motion in one direction or the other could be aided by a spring. It may be desirable in some cases to use damping mechanisms.

OPERATION The workpiece 4 may start as a smooth copper cylinder. The carriage 5 is initially positioned so that the hammers 22 engage the workpiece 4 near one end or the other (i.e., in either position 31 or position 33 of FIG. 4), and the carriage 5 is driven in a direction to move the hammers gradually toward the other end. For manufacturing a projection screen of the type described, it is preferred to make the carriage advance substantially one tool width for each rotation of the workpiece 4. The presently preferred cross-sectional dimensions of the hammers for that particular purpose are 0.020 by 0.020". If that is done, then the finished workpiece appears as shown in the upper part of FIG. 6, with contiguous rows of lenticules 30.

Since the rotation of the workpiece is not exactly synchronized with the operation of the hammers 22, nor with the movement of the carriage 5, the successive rows 30 will not necessarily be aligned with each other, as they appear in FIG. 6. There may be lateral steps of equal magnitude between each pair of successive rows. On the other hand, the relative positions of the successive rows may be completely random with respect to one another. The tips 22a, 22b, 220 of the hammers 22 are spaced apart by an even multiple of the tip widths. As best seen in FIGS. 5 and 6, there are four tip widths between each pair of successive tips. Thus, as the hammer is reciprocated against the workpiece, the first tip 22a first engages a smooth spot in the surface of the cylindrical workpiece 4 and makes a small dent therein. Five reciprocations of the hammer later, the second tip 22b engages the same indentation and makes it slightly deeper. Finally, five recipro-cations of the hammer later, the tip 220 engages the same indentation and deforms the metal into its final contour. The differences between the depths of the dents are exaggerated in FIG. 6 to facilitate illustration. Actually, the first dent will be substantially wider in FIG. 6 than is shown, and the second dent is, of course, intermediate in width between the first and third,

Depending upon the results desired, the number of hammer tips may be made greater or less than three. However, for the purposes of a projection screen embossing roll, it is presently preferred to use three hammer tips.

As the carriage moves from one end to the other of the workpiece 4, the plate 16 is tilted at varying angles because of the engagement of the roller 25 with the guide rail 26, as best seen in FIG. 4. If the carriage starts at the left end of that figure, at the position indicated by the numeral 31, the plate 16 is tipped so that the hammers strike the workpiece at a substantial angle, about 15, as shown at 32 in FIGS. 4 and 7. As the carriage moves along the workpiece, it reaches the position shown in full lines in FIG. 4 where the path of the hammer makes an angle of 90 with respect to the workpiece surface. As the carriage continues along the workpiece, it reaches the position shown at 33 in FIG. 4, where the hammers are tilted, in the opposite direction from their position at 31 and make an angle with the workpiece which is displaced from the perpendicular about 5.

Although the guide rail 26 is illustrated as straight, and as having a constant gradient, it should beunderstood that this contour and gradient are selected for the purpose of making an embossing roll to produce a projection screen. If the embossing roll is intended for other purposes, e.g., for making ornamental material, the guide rail may have linear or non-linear curved or angular contours. It may even become desirableto use such a curved or angular contour to make an embossing roll for projection screens. Furthermore, the positions of the ends of rail 26 could be varied as the operation progresses, according to any suitable predetermined program.

It is necessary that the workpiece 4 be of a material softer than the material used-for the hammer tips 22a, 22b, 220. It is presently preferred to-use copper for the workpiece and tungsten carbide for the hammer tips. However, other circumstances may dictate the selection of other materials. 1

The apparatus illustrated advances the hammer tips along a helical path over the workpiece surface. Alternatively, the hammers may remain in a fixed position while the workpiece rotates one or more revolutions, after which the hammer assembly may be stepped or indexed forward along the workpiece. To produce an embossing for making projection screens, such an indexing mechanism must be highly accurate, and hence expensive. For that reason, it is preferred to use the helical advance of the hammers. However, in other circumstances, e.g., for producing embossing rolls for making ornamental sheet material, such accuracy may not he needed, and a stepped advance of the hammers may be entirely satisfactory.

After the surface of the workpiece 4 has been completely contoured by the apparatus illustrated, it may be plated with chromium or other hard material, to provide a durable working surface. I

FIGS. 8-9

These figures illustrate amethod of manufacturing a projection screen, as shown in FIGS. 10 and 11, from an embossing roll made from the workpiece 4 of FIGS 1-7.

A finished embossing roll 35, made from the workpiece 4, may be used in a conventional embossing process illustrated somewhat diagrammatically in FIG. 8, where thermoplastic strip material 36 is being fed from a supply reel 37 through a heater '45 and thence into the nip between the embossing roll 35 and a backup roll 39. Either or both of the rolls 35 and 39 may be cooled. The strip then passes through a pair of cooling rolls 40 and onto a takeup reel 41. As the material passes the heater 45, it is heated to the point where it becomes plastic. The embossing roll 35 is then effective to form the top surface of the material in accordance with the pattern on the embossing roll. Since either roll 35 or 39 is cooled, it is effective to set the material.

The plastic material to be embossed may be either supported, i.e., backed by a sheet of fabric such as cotton duck, or it may be unsupported, in which case it is referred to as a film. After the material is embossed, it has applied on its embossed surface a coating of generally specular, slightly diffuse reflective material. It is preferred to use aluminum for this coating and to deposit it by means of a vapor deposition process. The metal coating applied to the surface of the plastic material should be thick enough to be substantially opaque, i.e., about three to seven-millionths of an inch thick.

As an alternative from o coating, a silver coating deposited by chemical precipitation, such as any suitable conventional mirror coating process, may be used. In that case, the thickness should be from sixto ten-millionths of an inch.

The screen may be cut into suitable lengths. The sides of the strip as it passes through the embossing roll form the top and bottom edges of the screen in its finished form. The horizontal dimension of the screen is therefore dependent simply on the spacing between transverse cuts in the embossed strip material.

FIGS. 10l1 These figures illustrate a projection screen 38 constructed from an embossing roll made with the apparatus and methods described above. The particular screen illustrated is intended for use in homes, schoolrooms, or the like, when the area in which the audience is located is at approximately the same horizontal level.

The screen 38 is described in detail in the copending application of Lucas and Hurd, mentioned above.

The reflecting surface of screen 38 is formed of a large multiplicity of reflecting lenticules, some of which are indicated by the reference numerals 40, 41, 42, 43 and 44.

The lenticules are arrayed in horizontal rows. In each row,

all the lenticules are tilted at the same angle relative to the vertical. For example, in the specific screen illustrated, each lenticule 44 in the top row, is tilted at an angle of 15 with its top edge forward with respect to its lower edge. The angle of tilt in this row is determined by the angle 32 in FIG. 7. The tilt decreases linearly and progressively from each row to the next down the screen, so that the tilt of the lenticules 43 is approximately 10. The lenticules 42 are tilted about 5 and the lenticules 41 have a tilt of 0. The lenticules 40, in the bottom row of the screen, are tilted 5 in the opposite sense, with their lower edges outward and their upper edges inward.

It should be noted that the position of the 0 level in FIG. 10, does not correspond to the full line position of the carriage 5 in FIG. 4, Where the arm 20 is in an angular position to produce lenticles of 0 tilt. This difference was introduced into FIG. 4 to facilitate illustration, and avoid overlapping of the full line and dotted line positions of carriage 5.

Furthermore, although the sequence of tilt angles shown in FIG. 10 is particularly suitable for screens where the audience is located substantially at one level, as in homes and classrooms, other sequences would be used where the screen is to be used for audiences having a greater vertical distribution, as in theaters and auditoriums.

It is desirable to have the largest dimension of the lenticule not substantially greater than about OLOQO. If the lenticules are constructed according to these criteria, i.e., small size, and slightly diffuse reflecting surface, then random irregularities in the formation of the lenticules are not visible to the observer. In the first place, each individual lenticule is too small to be distinguished by an observer at the usual viewing distance. The use of a slightly diffuse reflecting surface aids in concealing any defects in the lenticules.

While I have shown and described a preferred embodiment of my invention, other modifications thereof will readily occur to those skilled in the art, and I therefore intend my invention to be limited only by the appended claims.

What is claimed is:

'1. Apparatus for forming a workpiece, comprising:

(a) means for rotating the workpiece about an axis;

(b) a carriage movable parallel to the axis; and

(c) means for driving the rotating means and the carriage concurrently;

wherein the improvement comprises:

(d) a plurality of tools mounted on the carriage and spaced peripherally of the workpiece;

(e) reciprocating tool drive means mounted on the carriage and operable cyclically to separate the tool means from the workpiece and then to move the tool means against the workpiece; and

(f) means connecting the workpiece driving means in timed relation with the reciprocating tool drive means so that the plurality of tools successively strike sub stantially the same spots on the surface of the workpiece.

2. Apparatus for forming a workpiece, comprising:

(a) means for rotating the workpiece about an axis;

(b) a carriage movable parallel to the axis;

(c) means for driving the rotating means and the carriage concurrently; and

(d) tool means mounted on the carriage; wherein the improvement comprises:

(e) reciprocating tool drive means mounted on the carriage and operable cyclically to separate the tool means from the workpiece and then to move the tool means against the workpiece; and

(f) means to vary the angle of the path of movement of the tool means with respect to the axis of rotation of the workpiece.

3. Apparatus as defined in claim 2, including means for progressively varying said angle as the tool means travels from end to end of the workpiece.

4. Apparatus as defined in claim 3, in which said means for progressively varying the angle comprises:

(a) pivot means fixed on the carriage and having a pivot axis aligned with the working face of the tool means at the point where it strikes the workpiece;

(b) a plate rotatable on the pivot means;

(c) a follower mounted on the plate and spaced from the pivot means;

(d) elongated guide rail means extending generally parallel to the workpiece and adapted to be engaged by the follower, said guide rail being effective to control the angular position of the plate on the pivot means; and

(e) means on the plate supporting said reciprocating tool drive means.

5. Apparatus as defined in claim 4, including means for adjusting the position of the guide rail means to change said progressive variation.

6. Apparatus as defined in claim 5, in which said adjusting means comprises:

(a) means for independently adjusting the height of the opposite ends of the rail.

7. Apparatus for indenting the surface of a cylindrical workpiece to form an embossing roll for the production of projection screens, comprising:

(a) means for rotating the workpiece about its axis;

(b) a carriage movable parallel to the axis;

(c) means for driving the rotating means and the carriage concurrently;

(d) tool means mounted on the carriage;

(e) reciprocating tool drive means mounted on the carriage and operable cyclically to separate the tool means from the workpiece and then to move the tool means against the workpiece with sufiicient impact to indent the surface thereof;

(f) means synchronizing the carriage driving means with the workpiece rotating means, so that the car riage progresses one tool width along the cylindrical workpiece for each revolution of the workpiece;

wherein the improvement comprises:

(g) a plurality of tools in said tool means, each tool having on one end a lenticular surface which contacts the workpiece; and

(h) means connecting the reciprocating tool drive means with the workpiece rotating means so that the tool means and the workpiece move in timed relation, so that the plurality of tools successively strike substantially the same spots on the surface of the workpiece.

v 8. Apparatus as defined in claim 7, including means to vary the angle between the path of movement of the tool and the axis of the workpiece.

9. Apparatus as defined in claim 8, in which said means is operable to vary said angle progressively from one end of the workpiece to the other.

10. The method of making an embossing roll, including the steps of:

-(a) rotating a cylindrical workpiece;

(b) hammering the surface of the workpiece at an axially and peripherally limited locality thereof to produce indentations therein; and

(c) moving said locality lengthwise of the workpiece; wherein the improvement comprises:

(d) carrying on the hammering during continued rotation of the workpiece;

(e) moving the hammer lengthwise of the workpiece concurrently with rotation of the workpiece; and

(f) changing the angle between the path of movement of the hammer and the axis of the workpiece, as the hammer moves lengthwise of the workpiece.

11. The method of claim 10', wherein the change in the angle is progressive and linear.

12. The method of claim 10, wherein the change in the angle is non-linear.

References ited UNITED STATES PATENTS 372,669 11/1887 Gowen 7276 1,695,617 12/1928 Teissere et al. 7276 2,798,387 7/1957 Woodworth 7276 3,285,046 11/1966 Mellen et al. 7276 3,311,548 3/1967 Brown et al 20451 CHARLES W. LANHAM, Primary Examiner LOWELL A. LARSON, Assistant Examiner 

